The gram negative bacterium Legionella pneumophila is the causative agent of Legionnaire's disease, a severe pneumonia that particularly affects immuno-compromised individuals. Legionella is able to enter alveolar macrophages, evade destruction by the host cell endocytic pathway and replicate within an ER-derived organelle to cause disease. Recent work indicates Legionella injects proteins into the host cell via a type IV secretion system encoded by the Dot/lcm genes. These injected proteins, termed translocated effectors, are believed to subvert host cell membrane trafficking machineries to create an organelle permissive for bacterial growth. The first aim of this research proposal is to identify new Legionella translocated effectors using a genetic screen designed to assay for inhibitors of ER-to-Golgi transport. Next, the function of the newly identified effectors during infection will be characterized using genetic, biochemical, and cytological approaches. Finally, the host cell targets of the translocated effectors will be determined using yeast two-hybrid approaches. Together, the identification and characterization of new translocated effectors may provide new targets for therapeutic intervention. [unreadable] [unreadable] [unreadable]